Pietta cylinder bore vs. bbl bore

You're going to have to experiment. Since you can't very well mike a round ball (well, you can try, and maybe succeed, but it's a pain), you'll have to go by the age-old "ring o' lead method." If you don't shave a ring when loading, the ball is too small. .457 ball into a .455 cylinder sounds to me like you might have a problem.

Did you actually slug the barrel to get that measurement, or did you do it with calipers?

Lowshot;

I wouldn't send it back. Usually pistols that fire lead bullets do better with a "step down" from the cylinder throat to the bore. The purpose of the forcing cone (the end of the barrel that almost touches the cylinder) is to ease the transition for the larger ball into the tighter barrel. This "squeezing" effect makes sure that the lead ball grips the rifling thoroughly, which leads to good accuracy.

Ideally, for cartridge revolvers that shoot cast lead bullets, you'll want a bullet .001 above the cylinder throat diameter. Further, you'll want a bore that's .001 or maybe .0005 below the cylinder throat diameter to get the desired "squeeze" effect.

Although you're pistol has quite a difference, I don't think that will matter much. Lead is very pliable and you should get good results.

My guess is that you'll have a great shooter.

One last thing. Are you sure you're measuring the slug from your bore correctly? I don't know, not having my Pietta handy, but how many lands and grooves are there? S&Ws are notoriously hard to measure since they have an odd number of lands/grooves. This means that very expensive V calipers are needed to measure the slug to get the true groove diameter. Pietta's may be the same way.

Good luck.

-John

Maybe the bore and muzzle is slightly choked by design.
Some guns well known for their accuracy reportedly are, although sometimes that specific information is a "trade secret". Anschutz is one of those companies, and it was written that only their most loyal employees are even allowed into their barrel making room, since it's all hush hush and very secretive how they produce barrels to obtain optimum accuracy.
I believe that air rifle muzzles are more commonly choked too.
I recall a well known muzzle loader barrel maker who said that the inches leading up to the muzzle are more important for attaining good accuracy than the breech end is.
With all the new production equipment and methods, maybe this is one of the reasons why more recent production Pietta's seem to exhibit better accuracy...

The usual problem in the past was that the chambers were undersized for the bore. During the loading process the ball/bullet was swaged too small for the bore, and accuracy suffered. Apparently the Italian makers are addressing this issue. I wouldn't return the revolver without trying it out first. You may find that it's exceptionally accurate.

If the barrel isn't properly throated you may need to have that done, but otherwise I'd bet that this gun will be a shooter! Your lead will get plenty o grip on the rifleing as it passes through the barrel which should make it a very accurate weapon.

Having a bore slightly smaller than the chamber diameter is a bonus for accuracy, but the chambers miking at .455 seems a bit excessive. The usual recommended ball size for Pietta's is .451 or .454. Try the .457's and see if they shave a ring. If they don't, I'd send it back. If they do, it'll probably be a great shooter! Good luck.

Lowshot, what do you mean by "bore"? When you measured the slug did you measure the widest diameter carefully? What I'm gettin at is that it's the grooves diameter of the barrel you want to measure and not the top of the lands. How old is your gun? New? If yer lands(bore) are .445 then the groove diameter of the barrel would be close to the chamber diameter. That would be good especially if the chambers were equal to the grooves of the barrel. If you have as Pietta then is it the standard model or the "Shooters" model with the progressive rifling? The "Shooteres Model" comes out of the box with equal chambers and barrel grooves.
Some one stated that the chamber throats of cartridge revolvers should be smaller than the bullet diameter. I don't think that is right. The chamber throat should be equal or .001-.002 bigger than the bullet. The bullet should be equal to the barrels grooves or .001-.002 bigger for lead bullets. The jacketed bullets are sized at .451 so they are at least .001 smaller than the grooves so the jacket doesn't stick in the barrel and the lead core exits. A cap and ball likes the ball to be .005-.010 bigger than the chambers to swag in there tight. You can get by with a ball just .002 bigger than the chambers ifin you compress with the loading lever some to bump up the ball in the chamber to tighten it. If the balls don't back out with recoil it's fine. Anywhooo....the revolvers come out of the box with chambers smaller than the barrel grooves,unless they are changing that. I've found that the revolvers like the balls,therefore the chambers that swag the balls, to be equal to the barrel groove diameter or .001-.003 larger. Anywhooo...slug the barrel again and use two dowel rods at each side of the ball when in the barrel and wack it to ensure the ball is really filling the barrel grooves. Measure the widest point on the lead when it comes out of the barrel. Calipers can work if you are very carefull to not squish the corners of the lead lands on the ball. The lands on the ball that slugged the barrel is what to measure. The calipers will be on the very edge of a land on one side of the ball and the corresponding edge on a land on the other side of the ball. Just poke around and find the widest point. Carefully. There is a very small area that will show the diameter of the lands on the slug and that shows the barrel diameter in the grooves of the barrel. I kind of doubt the Pietta people would be making the revolvers with a chamber .010 over the barrel grooves. Maybe but I kind of doubt it. That is kind of tight and I'd think the revolver would shoot like a revolver does when the ball or bullet is too tight. Erratic. Like a revolver does when the crown is out of wack.

Side note....Parmamoon left me a message and my e-mail is screwed on this computer so I figure my reply won't go out. He should call 740-824-5566.

Hmmm. You folks seem to almost be taking those BP revolvers seriously, when the makers know they are turning out toys.

Jim

the usual pietta measurements over a long period of years are .448-.449" with the bore the same or a little smaller. They are tighter than the ubertis. I'm sure you are better with a caliper than I am but it is hard to measure the chamber mouths with a caliper. Might double check as most piettas are good for .451 balls where as they often creep in ubertis.

Hmmm. You folks seem to almost be taking those BP revolvers seriously, when the makers know they are turning out toys

Click to expand...

I almost dropped my pacifier when I read that one...you called my toy...I mean my gun...a toy. That's like saying football is a game. Well, it IS a game, but...
Anyways, I looked up "toy" in my Ninja Turtle Dictionary. A toy is "an object for children to play with." Well, OK, you got me there...I never grew up.
Also, "a thing very small of its kind." Well, they're pretty true to the original sizes.
And, "something of no real value." That depends...
"The difference between men and boys..."

Toys? These "toys" can kill a person very easily you know. The manufacturers don't think they are turning out toys, people like to shoot something that was part of history. The loud boom and all the smoke makes it attractive. I have more black powder guns than modern ones. Just because the gun isn't modern doesn't make it a toy; no gun should ever be considered a toy, no matter how old or what powder they use.

I think you misunderstood Jim. I think he's delighted that black powder revolver shooters are getting serious about accuracy and related issues. Also firearms that are purchased and used for non-weapon purposes are often refered to as "toys," with no disrespect intended.

Maybe you are right. Can't hear tone of voice ect. on the net!

I took it as a joke - that's why I was funnin' with Jim. But it does bring up a good point, or at least an interesting one. Also, the words "replica, reproduction and original" come into question, and the concept of a "real Colt" if it's a 3rd Generation or Signature Series.
But, if I see Jim on the playground, I might steal his lunch money for making fun of my toy...ah, gun (unless he's bigger and older than me).

I'm with Jim on this one. Each and every one of my black powder guns, and most of my more modern ones are toys. They're the toys I love to play with the most and give me the most pleasure. Like anyone who really loves their toys, I want the entire collection!

I'll help if you give me 50%.

I don't mind people saying "I got a new 'toy'" or whatnot, but I don't think they should ever be considered a toy. Just took it the wrong way I guess. Sorry Jim!

If you have one, you can call it a toy. People that don't have guns and call them toys really tick me off. My anti-gun neighbor called me a "gun nut" because I have a bunch of BP revolvers. I pointed to his golf bag and asked him what each club cost - each one cost more than a BP revolver. So, he's a golf nut. At least shooting is a sport...

you can get fine accuracy with balls that mearly swage in and don't cut a ring. The problem comes when the ball move forward under recoil.

Yeah, being able to push the ball in is a problem. That loading lever is nice and long because you need the leverage. A ball that pushes in with no effort is a safety hazard. Since .457 is getting into "pretty dang big" territory with a .44, I would think seriously about sending it back.

I'd mike those balls or try some from a second source before I made any firm decisions. The box or mold they came from may have been mis-labelled.

Steve